My 80M half-sloper also exhibits a very wide 2:1 SWR bandwidth. If I
recall, it's below 2:1 from 3.5 - 3.8 MHz. It's resonant (min SWR) around
3.6 MHz. The sloper wire is about 67 feet long, and it's connected to the
64-foot tall tower at about 50 feet, below a triband Yagi and 40 M rotatable
dipoile. I also have gotten better signal reports from local ops using this
antenna than when I had used my 160M inv L wire. My radial system is seven
radials: five are 100 feet long and two are less than 35 feet.
My suggestion to you would be to get on the band and enjoy your
sloper's performance. Don't think about it too much; you might be tempted
to <improve> it's performance!
Gene Smar AD3F
From: Jose M. Valdes R. <email@example.com>
To: firstname.lastname@example.org <email@example.com>
Date: Tuesday, February 18, 2003 12:21 PM
Subject: [TowerTalk] 1.8 MHz half sloper using tower VSWR question
>I'm new to this list but I have being reading your posts at the archives
>in contesting.com and I must say that I enjoy them very much.
>Now, I have a question.
>After 9 years I'm getting back on the low band, so I built an antenna
>for it. This antenna is half-sloper using a tower with the following
>The tower is guyed aluminum with a height of 15 meters (+- 49.2 feet)
>including the top mast which is 6 meters (+- 19.7 feet) in length, this
>mast is the support for 3 monoband Yagis that provides the capacitance
>hat and installed in the following order from bottom to top, a 4
>elementes for 20 meters on a 11 meters (+- 36 feet) boom, a 5 elements
>for 6 meters on a 6 meters (+- 19.7 feet) boom, and a 2 elements for 40
>meters on a 5 meters (+- 16.4 feet) boom.
>I attached 8 radial to the base of the tower of random length as was
>allowed by the available space.
>Also I ran a ground wire from the base of the tower to my grounding
>system, which consist of a 280 square meters (+- 3014.9 square feet) of
>a grid of squares of 2 x 2 meters (+- 6.6 x 6.6 feet) constructed with 2
>inches galvanized pipe and buried 3.3 feet below the ground.
>The half sloper consist of 39 meters of number 14 wire in a sloping
>horizontal "L" shape and attached at the 35 feet point with a very short
>insulator (2 inches) and very short (2 inches) wire from the braid of
>the RG-8 to the tower, you can see a diagram at the URL below.
>This antenna is showing a very unusual bandwidth that spans from 1.800
>MHz to 1.950 MHz with a VSWR of 2.0 to 1 or below and a minimum of 0.2
>to one on 1.870 MHz and 1.880 MHz, this seems to be unusual for these
>band, since I don't recall having any previous 160 meters antenna with
>such a large bandwidth, below is the VSWR table.
>1.800 2.0 to 1
>1.810 1.7 to 1
>1.820 1.6 to 1
>1.830 1.4 to 1
>1.840 1.3 to 1
>1.850 1.3 to 1
>1.860 1.1 to 1
>1.870 0.2 to 1
>1.880 0.2 to 1
>1.890 1.1 to 1
>1.900 1.2 to 1
>1.910 1.4 to 1
>1.920 1.5 to 1
>1.930 1.7 to 1
>1.940 1.8 to 1
>1.950 2.0 to 1
>At 1.870 MHz and 1.880 MHz the impedance if of 47 ohms.
>Now to my questions.
>Is this bandwidth possible for a half sloper?
>And of not, what may I have done that is wrong?
>2 nights ago I talked to YV4GD, in Valencia, about 200 KM form my QTH
>and we both running 100 watts and the signals at both ends were 59 + 10
>73/DX Jose M. Valdes R. (Joe), YV5LIX.
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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